Imma Perfetto
Cosmos science journalist
New research suggests that 2 massive canyons on the Moon were carved out by streams of impacting rocks travelling at about a kilometre a second.
The canyons, Vallis Schrödinger and Vallis Planck – at 270km long and 2.7km deep, 280km long and 3.5km deep, respectively – are comparable in size to the Grand Canyon in the US.
“Whereas Arizona’s Grand Canyon was carved by water over the last 5-6 million years and from integrated paleocanyons that formed over 70 million years, the Moon’s Vallis Schrödinger and Vallis Planck were carved by streams of impacting rock in less than 10 minutes,” write the authors of the new Nat
They are among the many canyons and ravines that surround the 3.81-billion-year-old Schrödinger impact basin, and until now scientists weren’t sure exactly how they formed.
A new Nature Communications study suggests they were shaped by streaks of rocky debris, also known as ejecta rays, thrown out during an asteroid or comet impact that formed the basin.
The researchers estimate that the energy needed to produce these grand canyons on the Moon was massive: “…more than 700 times larger than the total yield of US, USSR, and China’s nuclear explosion tests, and about 130 times larger than the energy in the global inventory of nuclear weapons.”
They used photographs of the Moon taken by NASA’s Lunar Reconnaissance Orbiter to create maps of its surface. Using these, they calculated the flow directions and speed of the debris ejected during the impact event.
They could then model how the ejecta rays were formed.
The team proposes that the canyons were carved out of the lunar crust in less than 10 minutes by ejecta travelling between 0.95-1.28km per second.
The average size of the ejecta fragments that carved Vallis Planck would have been less than 2km in diameter, while those that carved Vallis Schrödinger could have been as large as been 2.3-5.2 km in diameter.
The calculations suggest that most of the excavated debris was distributed asymmetrically, which points to a shallow impact trajectory in the direction away from the south pole.
The researchers say that the Schrödinger impact trajectory has important implications for the pending Artemis missions to the south polar region.
“The rim of the Schrödinger basin is within 300 km of the south pole and within 125 km of the Artemis exploration zone, which is the first destination of Artemis astronauts,” the authors write in the paper.
“The asymmetric ejecta distribution implied by Schrödinger’s crater rays suggests there is less Schrödinger impact ejecta covering candidate landing sites and, thus, astronauts and robotic assets will find it easier to sample [the South Pole–Aitken basin] and underlying primordial crust samples.”
